I am a descendant of Milton Brown [born about 1797] who married Kizzy [Kesiah, Kizia] Hooper in 1820/1 in Haywood County, NC. Kizzy was a younger sister of Mary Hooper. I've been studying these Brown/Hooper families since the mid-1980s.

Re: vital stats on the Hooper parents.
The sisters' father Absolem Hooper died on 9 Dec 1845, per federal pension application records.
Their mother Sarah received her widow's pension payment for March 4 1859 but not for the next payment on September 4, 1859. She is not listed on the 1860 mortality schedule (which was a record of deaths occurring between June 1, 1859 and May 31, 1860). Nor is she listed on the 1860 census (which should have included her if she had lived in a household on June 1, 1860). These facts suggest that Sarah probably died sometime in 1859 after March, and probably before June.

Extensive study of the many records for Absalom Hooper makes me believe his birth occurred in 1764/5. His birthplace was near the mouth of the Green River on the Broad River - which places his birth somewhere in what is eastern Polk County, NC near its boundary with Rutherford County and close to the state line with South Carolina. Although his parentage remains unknown, there were adult Hoopers associated with that area around the time of his birth.

Henry Brown died 14 November 1845 and is buried at Ivy Mount Cemetery in what is now Towns County, GA. His fieldstone marker failed to give his birth date, so little is known of his exact birth year and of where he was born.

Regarding relatives on the Brown side.
Milton Brown's father remains unknown. But....
There IS circumstantial evidence to suggest the two Hooper sisters, Mary and Kizzy, married Brown brothers.
In part, this suggestion is based on the similar migration pattern for each Brown household from western NC into north GA. We know that Henry was born between 1800 and 1810, based on his 1830 census entry in Haywood County. In that year, Absalom Hooper was three names above that of Henry. Right after Henry were a David Brown and a John Brown [aged 20-30]. It's not obvious from the census whether David Brown was aged 20-30, or 60-70, since there was a man of each age in the household headed by David Brown. The older man in the home was old enough to be the father or uncle of several of the Browns who inhabited Haywood County in the 1830s.

There was a David Brown [born around 1795] who lived in Haywood County in 1832 [according to a son's claim of his birthplace in a biography]. David Brown migrated to Union County, GA and is listed on a special census in 1834 there. Milton Brown was also on that 1834 census, though Milton returned slightly north to NC in 1840, before going back to GA before 1850. By 1850, this David Brown had moved on to Cherokee Co., GA. His wife soon died, and David and offspring moved to Arkansas where he died 1858.
Two things are significant about this David Brown -
1) his wife was the former Rhoda CHASTAIN born about 1807 SC and
2) male descendants of David Brown are close, though not exact, y-DNA matches to a descendant of Milton Brown. This near match suggests these Browns probably have a common male ancestor who lived sometime before 1795.

Fact #1 is significant for Mary (Hooper) Brown's offspring because she had two sons born out of wedlock before her 1826 marriage to Henry Brown. Those sons used the surname Hooper, but were acknowledged by their father - John CHASTAIN. [And besides this Chastain connection, Mary's elder sister Nancy Hooper had married Benjamin Chastain in 1812.]

Now given that Mary Hooper had two out-of-wedlock sons before her marriage in 1826, she would have been less marriageable than other women of similar age in the area. Thus, it seems likely that her husband already had some family and locational interaction with her - probably by Milton Brown's marriage into the Hoopers and perhaps by Rhoda (Chastain) Brown's involvement with Chastain kin.

There is one more yDNA close match, with a descendant of William Avery Brown (born 1809) whose yDNA is close to that of the Milton Brown descendant. The match is close enough to suggest that William A Brown and Milton Brown shared a common male ancestor sometime before 1797.

Just like the other Browns I have mentioned, this William A. Brown also passed through Union County, GA at the same time that Milton Brown and your Henry and Mary (Hooper) Brown lived there. William married in Union County in 1834, so was one of the earliest European settlers of that area.

There seems to be a strong chance that William A. Brown was a close connection to Henry Brown. Leeland Robert [or Robert Leland] Brown was the eldest son of Henry and Mary (Hooper) Brown. In 1850, he lived with his mother still in Union County. However, he married and moved on to Fannin County, GA by 1860. For the census in that year, he lived just 7 households distant from William A. Brown. This proximity suggests a strong possibility that the older man, William A Brown, had been a close relative to Leland's father Henry Brown.

So, William A Brown shared a common male ancestor with Milton Brown, and there is locational evidence suggesting William was closely related to Henry. This combo also supports the idea that Milton Brown (husband of Kizzy Hooper) was closely related to Henry Brown (husband of Mary Hooper).

One way for descendants of Henry Brown and Mary Hooper to determine whether Henry was a close relative of either Milton or David or William A Brown would be through yDNA tests done by FamilyTreeDNA.com - the price right now is about $169 for a 37-marker test, but there are sales throughout the year where the price is lower. The test would have to be by a man who is a direct, male-to-male descendant of Henry Brown. So, for example, the Richard Osborn Brown you mentioned would be a good candidate, since there is direct descent from Rev. Absalom Marion Brown. And Absalom Marion Brown is listed as a "minor heir of Henry Brown" in Towns County court records, so has legal, verifiable descent from Henry.

Hope this helps.
AnneG